1. Field of the Invention
This invention relates to certain amorphous compounds that are unique in their applications as remineralizers of caries lesions, cavities and root erosions of the tooth and desensitization of dentin. These amorphous compounds when further containing a fluoride compound can also be used for topical fluoridation of the teeth. When used for either fluoridation or mineralization these compounds prevent further tooth decay and actually restore the lesions caused by dental caries. This invention particularly involves the use of amorphous calcium compounds, the strontium substituted counterparts to the amorphous calcium compounds, and incorporation of magnesium to the amorphous compounds for the treatment of dental tissue.
The invention is further directed to methods for delivering these amorphous compounds to dental tissue. It has been found that carbonated solutions are especially effective in such delivery and may be used to control the pH and stability of the solutions. These carbonated solutions precipitate calcium and/or strontium compounds when applied under oral conditions due to the escape of dissolved carbon dioxide and the increase in the pH of solutions.
2. Description Of The Prior Art
When an incipient lesion or cavity develops on the surface of a tooth, the dentist traditionally fills the cavity that forms. This procedure may prevent the decay from spreading further, but does not restore the tooth to its original state.
Dental lesions and cavities, exposed roots and dentin sensitivity develop due to the loss of tooth minerals. Tooth minerals are apatites that are impure forms of hydroxyapatite, Ca.sub.5 (PO.sub.4)OH. Recently, the processes of topical fluoridation and mineralization have been used and developed to treat these dental maladies. The objectives of topical fluoridation and mineralization are to deposit fluoride and apatite on and into the tooth, thus preventing further tooth decay, restoring the tooth or obturating the dentinal tubules.
Three approaches have been used for topical fluoridation of the tooth. The first introduces simple fluoride-containing compounds onto the surface of the dental enamel. The second one introduces acidulated phosphate fluoride, which involves the dissolution of some tooth tissue and precipitation of calcium fluoride. The third procedure involves an intermediate product of dicalcium phosphate dihydrate which then converts to fluorapatite.
A considerable amount of research has recently been directed toward the remineralization of dental lesions. In the area of remineralization of dental tissues, there are at least three approaches. One uses a metastable fluoride-containing calcium phosphate solution supersaturated with respect to fluorapatite and hydroxyapatite which will form apatite slowly when applied. A second uses combinations of sparingly soluble calcium phosphates with crystallized tetracalcium phosphate and at least one different calcium phosphate in slurries and paste forms. Such an application is disclosed in U.S. Pat. No. 4,612,053 to Brown, et. al. A third uses potassium oxalate solutions to obturate the dentinal tubules as disclosed in U.S. Pat. No. 4,538,990, issued to Pashley, et. al., and U.S. Pat. No. 4,057,621, issued to Pashley, et. al.
These prior art mineralization methods are characterized by several practical problems. When a supersaturated solution of low calcium and phosphate concentrations is used, the remineralization process is extremely slow. The remineralization process is, in fact, so slow that an inconvenient amount of time is required for its completion. Another problem with these methods is that as the apatite is deposited upon the teeth, the pH's of the treating solutions change. Such a change can make the solution too acidic, creating the possibility of damaging the dental tissue.
Therefore, there remains a need for a treatment which achieves rapid remineralization of teeth similar to the natural process of biological mineralization, without the dissolution of the existing dental tissue.
Although the prior art does not teach the use of amorphous calcium compounds for remineralization of teeth, it does refer to amorphous calcium phosphate as an aspect of the investigation of natural bone formation. See Synthetic Amorphous Calcium Phosphate and Its Relation to Bone Mineral Structure, Posner and Betts, ACCOUNTS OF CHEMICAL RESEARCH, Jan. 31, 1975; An Intermediate State in Hydrolysis of Amorphous Calcium Phosphate, Tung and Brown, CALCIFIED TISSUE INTERNATIONAL, 1983. This use, however, is significantly different from the present invention. Bone tissue is 50% organic material and 50% inorganic material, whereas dental tissue is 90% inorganic. As such, significantly different factors affect the treatment of the different tissues.
The prior art further teaches the use of amorphous tricalcium phosphate as surgical cement in teeth and bones. See U.S. Pat. No. 4,684,673 issued to Adachi. Contrary to the present invention, Adachi teaches a filler or a cement, not a composition which reconstructs the dental tissue.
Moreover, strontium compounds have been used in dental preparations before. Topical application of 25% strontium chloride in aqueous solution has been used for desensitization with considerable success. Additionally, dentifrice with strontium chloride has been used to reduce the hypersensitivity of dentin commercially. But there is no teaching of any use of amorphous strontium compounds as dental remineralizers in the prior art.